1. Field of the Invention
The present invention relates to a motive-power transmission device for a vehicle comprising a torque converter having a pump which rotates as a unit with the crankshaft of an engine, a gearbox wherein one of gear trains is selected and put into operation, and a clutch for cutting off the transmission of motive power between the input shaft of the gearbox and the turbine of the torque converter.
2. Description of the Related Art
Such motive-power transmission devices have been known to date as is disclosed in the Japanese Unexamined Patent Publication No. S47-40717.
In the motive-power transmission device of the above related art, the crankshaft and the input shaft of the gearbox are aligned with each other, and the torque converter, the clutch, and the gearbox are arranged in line. Such arrangement is preferable in case of a motive-power transmission device wherein the gearbox case is separate from the crankcase of the engine. However, if such arrangement is adopted for a motive-power transmission device wherein the gearbox is accommodated in the crankcase of the engine, the motive-power transmission device becomes large along the axial direction of the crankshaft and hence unsuitable for installation in relatively small vehicles. In case of an all terrain vehicle of a saddle type in particular, the distance between the right and left footrests becomes large, spoiling the riding posture if the axis of the crankshaft is disposed in the lateral direction of the vehicle. If the axis of the crankshaft is disposed in the longitudinal direction of the vehicle, the center of gravity of the vehicle moves forward, increasing the load on the front wheels and hence the steering force required of the rider.
In accordance with the above, an object of the present invention is to provide a motive-power transmission device wherein the gearbox is accommodated in the crankcase and which is compact in the axial direction of the crankshaft.
According to a first aspect of the present invention, there is provided a motive-power transmission device for a vehicle comprising a torque converter having a pump which rotates as a unit with the crankshaft of an engine, a gearbox wherein one of gear trains is chosen and put into operation, and a clutch for cutting off the transmission of motive power between the input shaft of the gearbox and the turbine of the torque converter. The crankshaft and the input shaft are journaled freely rotatably in the crankcase of the engine, and their axes are parallel to each other. The torque converter is mounted on one end portion of the crankshaft. The clutch is separated along the axial direction of the crankshaft from the torque converter and so mounted on one end portion of the input shaft that part of the clutch overlaps the torque converter as seen in the axial direction of the crankshaft.
In accordance with the first aspect of the present invention, the motive-power transmission device wherein the gearbox is accommodated in the crankcase can be made compact in the axial direction of the crankshaft because the torque converter and the clutch are mounted on the crankshaft and the input shaft, respectively, which are parallel to each other. In addition, because the clutch can be disposed close to the crankshaft, the motive-power transmission device is made compact in the direction orthogonal to the axis of the crankshaft.
According to a second aspect of the present invention, there is provided the motive-power transmission device of the first aspect of the present invention, wherein: the torque converter is mounted on one end portion of the crankshaft which protrudes from the crankcase; mounted on one end portion of the input shaft protruding from the crankcase is the clutch which is operated by oil pressure and disposed between the torque converter and the crankcase; and an oil feed pipe, which extends coaxially with the input shaft, by the torque converter and feeds oil to the clutch, is provided between one end portion of the input shaft and a cover which covers the torque converter and the clutch and is joined to the crankcase. Thus, the space by the torque converter is made use of to constitute the hydraulic-oil feed system for the clutch.
According to a third aspect of the present invention, there is provided the motive-power transmission device of the second aspect of the present invention, wherein a control valve for the clutch for controlling the oil pressure to act on the clutch is connected to the oil feed pipe and mounted on the cover. Thus, the clutch and the control valve for the clutch can be arranged close to each other and, thereby, an excellent responsiveness of the clutch to the workings of the control valve can be achieved.
According to a fourth aspect of the present invention, there is provided the motive-power transmission device of the second or third aspects of the present invention, wherein the clutch comprises: a clutch center which is coupled with a driven gear and rotates about the axis of the input shaft; the driven gear engaging a driving gear which rotates as a unit with the turbine of the torque converter; at least one first clutch plate which engages the outer periphery of the clutch center so as to prohibit the relative rotation between itself and the clutch center; at least one second clutch plate which is disposed so as to overlap the first clutch plate; a clutch drum which accommodates the first and second clutch plates, engages the outer periphery of the second clutch plate to prohibit the relative rotation between itself and the plate, and rotates with the input shaft as a unit; and a piston which is fitted in the clutch drum so as to be freely slidable to cause frictional engagement between the first and second clutch plates. Thus, the clutch having the relatively large clutch drum can effectively be disposed along the axis of the crankshaft, near the torque converter, without causing the clutch drum to interfere with the crankshaft.
According to a fifth aspect of the present invention, there is provided the motive-power transmission device of the fourth aspect of the present invention, wherein a first one-way clutch for transmitting the motive power from the input shaft to the clutch center is provided between the clutch center and the input shaft. Thus, the motive power of the gearbox can be transmitted to the torque converter when the engine brake is applied.
According to a sixth aspect of the present invention, there is provided the motive-power transmission device of the fourth or fifth aspects of the present invention, wherein: a second one-way clutch for allowing a stator of the torque converter to rotate in one direction is provided between the stator and the crankcase; the driving gear is disposed between the second one-way clutch and the torque converter, along the axial direction of the crankshaft; and the clutch is mounted on one end portion of the input shaft so that at least part of the clutch drum takes a position along the axial direction of the crankshaft and by and adjacent to the second one-way clutch. Thus, the efficiency of the torque converter can be improved by having the second one-way clutch allow the stator to rotate idly. Besides, the second one-way clutch with a relatively small diameter can effectively be disposed in the space between the clutch drum and the crankshaft, positionally corresponding to at least part of the clutch drum.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.